Add setting to disable automatic schema detection for matching YAML files and add "No JSON Schema" to schema picker

[shin19991207]

What does this PR do?

• Added setting to disable automatic schema detection for matching YAML files (See Add setting to disable automatic schema detection for matching YAML files yaml-language-server#1251)
• Made "No JSON Schema" option selectable in schema picker from the status bar

What issues does this PR fix or reference?

Fixes #245
Fixes #991

Is it tested? How?

• New automated tests
• Manual testing

[datho7561]

Looks good to me and works well!

Found some weird stuff in the schema picker that's probably unrelated and can be handled in a later PR:

1. If a YAML file has two schemas, there's a weird stack overflow on the server somewhere when trying to open the picker.
2. The picker doesn't appear in docker-compose.yaml files; I'm guessing the picker is registered for YAML files, and docker compose files are considered as a different language. I don't know if it's worth addressing this, since the schema should be correct?